A muscle disorder as presenting symptom in a child with mucolipidosis IV.

Psychomotor retardation and hypotonia were found in a 1 1/2 year old girl with bilateral corneal opacities. Very high levels of enzymes of muscular origin together with abnormal electromyograms and muscle biopsy lead at the time to the diagnosis of an unspecified muscle disorder. Twelve years later mucolipidosis IV (ML IV) was diagnosed in this child. She was then very retarded, ocular and neurologic deterioration were evident and enzyme levels were still very high. Only few patients affected with ML IV have been reported and all but one were very young; therefore it is important to add observations on the progression of the disease and on unusual clinical features like muscle involvement.